1. Technical Field
The present invention relates to an image correction apparatus, an image display system, and an image correction method.
2. Related Art
In recent years, high-performance image display apparatus, such as large-screen televisions and projectors, have achieved widespread use. In such image display apparatus, color reproducibility and image quality are considered more important. There is thus a strong market need for an image display apparatus that ensures “screen uniformity,” in which a pixel having the same signal value is displayed with the same color at any position in a displayed image.
On the other hand, there is an image display system that uses a plurality of image display apparatus to arrange a plurality of images contiguously or superimpose a plurality of images. Such an image display system can express an impressively huge image or a multi-color image that cannot be expressed by a single image display apparatus. Color reproducibility and image quality are also important in the image display system that arranges a plurality of images contiguously or superimposes a plurality of images. Although there is a strong market need for an image display system that ensures the “screen uniformity” described above, ensuring the “screen uniformity” is difficult due to product-to-product variation of image display apparatus that display respective images.
As the technology for ensuring the “screen uniformity” described above, for example, JP-A-2006-38976 and JP-A-2006-153914 disclose technologies for correcting in-screen color non-uniformity.
JP-A-2006-38976 discloses a technology for preventing generation of color non-uniformity in every possible grayscale in input data. The technology allows data on the input-output characteristics of an image display apparatus to be measured and correction data for reducing the difference between the input-output characteristics data and reference input-output characteristics data to be determined for each grayscale level.
JP-A-2006-153914 discloses a technology for correcting illuminance non-uniformity including color non-uniformity and brightness non-uniformity. In the technology, a brightness non-uniformity correction pattern and a color non-uniformity correction pattern are used to create an illuminance non-uniformity correction pattern table for a plurality of illuminance levels. The table is used to reduce the amount of brightness non-uniformity generation and the amount of color non-uniformity generation to reduce the amount of illuminance non-uniformity generation.
JP-A-2006-38976 and JP-A-2006-153914 disclose technologies for correcting color non-uniformity in a single image produced by a single image display apparatus, but do not disclose technologies for correcting color non-uniformity when a plurality of images are arranged contiguously or superimposed. Therefore, the technologies disclosed in JP-A-2006-38976 and JP-A-2006-153914 cannot disadvantageously ensure “image quality uniformity” in an image display system that arranges a plurality of images contiguously or superimposes a plurality of images.
Further, the technologies disclosed in JP-A-2006-38976 and JP-A-2006-153914, when used to correct in-screen color non-uniformity produced by a single image display apparatus, have the following problem:
That is, when the technologies disclosed in JP-A-2006-38976 and JP-A-2006-153914 are used to correct signal values of pixels in accordance with correction data or a correction pattern, the corrected signal values may become larger than a limit value set in the image display apparatus (maximum pixel value, for example) in some cases. In this case, the correction of the signal values is insufficient, and another color non-uniformity problem disadvantageously occurs in an image produced by a single image display apparatus.
Therefore, in the technologies disclosed in JP-A-2006-38976 and JP-A-2006-153914, correction has to be made in such a way that corrected signal values do not exceed a limit value set in the image display apparatus. Therefore, the technologies disclosed in JP-A-2006-38976 and JP-A-2006-153914 cannot perfectly eliminate color non-uniformity even in an image produced by a single image display apparatus or cannot sufficiently ensure “screen uniformity.”
Therefore, when the technologies disclosed in JP-A-2006-38976 and JP-A-2006-153914 are used to arrange a plurality of images contiguously or superimpose a plurality of images so as to display a single image, color non-uniformity disadvantageously occurs at boundaries between contiguous images or in the portion where images are superimposed.